if you don't want to go active (stupid reason anyway), go passive, but stick to the major brands (Duncans, etc.).

a good pickup can make a big difference if you have a poor rig (amp/effects).
just as a good rig can get you a decent sound even from mediocre pickups.
so what's it gonna be?

i don't consider the HZ's to be worth upgrading to.
(if you're stuck with a pair, it's another story, but not to go out and buy them)
but now we get into all that personal prefference thing...

my advice is to stick with top brands.
if you don't have the cache, change them only on one guitar...
or replace the bridge pickup...
(use this to try out more models (f.e. Invader, JB, Dime... ))

that is what i did with a cheap guitar that i took for firewood: replaced the bridge pickup and after a year (i was pleased with the result) i found it worthy to also replace the neck.
i still use it for rehearsal/backup. (i went Invader/59)